ADSORPTION MODES OF ACETONITRILE ON NI(111), NI(100), AND NI(110) - ASEMIEMPIRICAL THEORETICAL-STUDY

The features of several adsorption modes of acetonitrile on three sele cted faces of nickel have been investigated by means of extended Hucke l calculations on finite-size clusters. The present results are consis tent with the available experimental data on this system. The face for the stablest adsorption is the open (110) one, on which CH3CN prefere ntially adsorbs parallel to the surface with a binding energy greater than 30 kcal . mol(-1). On the (100) face, acetonitrile is less strong ly bound in the same eta(2) geometry. Lastly, on the (111) face, there is a competition between two geometries: one parallel to the surface and the other perpendicular. The underlying electronic effects have be en thoroughly analyzed and explained by the balance between stabilizin g two-electron interactions and repulsive four-electron ones.